Top US general Richard Myers has described an Amnesty International report on Guantanamo Bay as "absolutely irresponsible".
Gen Myers says the camp is a "model facility"
The human rights group last week described the US detention camp in Cuba as "the gulag of our time".
But Gen Myers said the US military treated detainees there humanely.
The Guantanamo Bay camp has been the focus of protests in the Muslim world, after allegations that guards had been disrespectful towards the Koran.
Speaking on the US television network Fox News, Gen Myers said the camp was "essentially a model facility".
He said 1,300 Korans had been handed out to detainees in 13 different languages and that prison staff had served up "the proper Muslim-approved food".
"I think I'd ask them to go look up the definition of gulag as commonly understood," he said of Amnesty's report.
Guantanamo Bay has received much attention recently as the result of a Newsweek report this month which said US guards had flushed a Koran down a toilet.
Newsweek has retracted its story, which sparked violent anti-US protests in Afghanistan, as well as demonstrations in Pakistan and Indonesia.
However, the US military has admitted to five incidents in which the Koran was mishandled by staff at the camp.
Gen Myers said the prisoners at Guantanamo were dangerous and the US was doing its best.
"How do you handle people who... who aren't part of a nation-state effort, that are picked up on the battlefield... that if you release them, or if you let them go back to their home countries, that would turn right around and try to slit our throats, our children's throats?" he said.
"The president said we'll treat people humanely and in accordance with the Geneva Convention. We're doing that."
He said the International Committee of the Red Cross had had access to Guantanamo "from the day we opened the gates".
"I mean essentially, they've (ICRC) been there the whole time. And we get good marks for the way we take care of people," he added.